Ember
As i said in a previous post which you probably ignored, why would you not make it a holiday where everyone has time to do stuff they enjoy?
And seriously, who in their right mind spends 7 days solid at a them park, and if that wasnt the plan (i expect it isnt) then there are other things to do where everyone can enjoy.
Eg
Day 1
Half day by the pool (pick somehwere with kids clubs / activities)
My kids similar ages when we went to salou. Dorada Palace and villa romana good for that. Eldest had a ball with activities. Twins pottered by pool.
Half day at the beach
Day 2
Day at theme park. Take turns with minding DD
Day 3
Beach / other activities / boat trip/ beach games /
Walks
Cannot even remember what else there is but we were never stuck.
You made your mind up to leave her behind before coming on this thread. You will find vinducation for some.
Many, like me, cannot see it as a decent way to treat a child.
Salou is a family centred place. You will see kids of all ages and will wonder why you left her at home. Lets hope its not pissing down at home and that she doesnt wonder where the hell her family has disappeared to.